Telephone-exchange system.



C. L. GOODRUM.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION flLE D MAR. 29. 1917.

1 ,275,0 1 6 Patented Aug. 6, 191 8.

//7 van/0r: Char/e5 1. 6005/91/01.

ERS ca. Punmuma, WASHINGTON o. c

UNITED STATES PATENT OFFICE.

CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHAN GE SYSTEM.

Specification of Letters Patent.

Patented Aug. 6, 1918.

Application filed Marcn29, 1917. Serial No. 158,197.

To all whom it may concern:

Be it known that I, CHARLES L; GooDRUM, a citizen of theUnited States, residing at New York,in the county of New York and State of New York, haveinvented certain new and useful Improvements in Telephone- Exchang'e Systems, of which the following is a full, clear, concise, and exact description. I

This invention relates to telephone exchange systems employing machine switching, and more particularly to automatic selector switches therein. 7

The object of this invention is to provide mechanical means whereby a selector switch, failing to find an idle trunk during its hunting movement, will be automatically restored to the beginning of the selecting movement, and again driven over such trunk group, this operation continuing until an idle trunk is found.

To accomplish this result, the selector, in the present embodiment of the invention, is provided with means attached to its shaft whereby the secondary holding pawl is withdrawn from its ratchet when the selector brushes move off of the last set of trunk terminals and allows thebrushes to be restored tothe beginning of their secondary movement. Means are also provided for keeping the circuit of the secondary magnet open until the shaft reaches its normal position, at which time the secondary pawl is restored into engagement withthe secondary ratchet and the selector brushes again driven over the group by the secondary magnet.

The invention will be more readily understood when' described with reference to the accompanying drawing, which is a diagrammatic representation of a calling subscribers telephone line extended to a first selector switch, only so much of the telephone exchange system as is deemed necessary for an understanding of the invention being shown." I y When the subscriber at substation A removes his receiver, a line finder F, of which only the brushes 1, 2 and 3 and terminals 4, 5, and 6am shown, is set. in motion to find the calling line. When the calling line has been extended to a first selector FS, the stepping relay 7 thereof is' energized over a circuit from grounded battery, right hand winding of relayv 7, side-switch arm 8, conductor 9, brush 1, terminal 4, conductor 10, sender 11, telephone apparatus at substation A, conductor 12, terminal 5, brush 2, side-switch arm 14, left-hand winding of relay 7 to ground. Relay 7 closes, at its front contact, a circuit for slow relay 15 from grounded battery, winding of relay 15, armature and front contact of relay 7 to ground. Relay 15, by attracting its armature, closes a break in the circuit of relay 16, which controls the escape magnet 21, and also closes a break in the circuit of the primary magnet 17 to the back contact of stopping relay 7.

The calling party now operates the sender 11 to transmit the impulses corresponding to the first digit of the wanted number. Upon each retraction of the armature of stepping magnet 7, an impulse is trans mitted to primary magnet 17 from grounded battery, winding of magnet 17, conductor 18, secondary off-normal contact SON, conductor 19, armature and front contact of relay 15, conductor 20, armature and back contact of relay 7 to ground. The slow relay 16 is energized .in parallel with primary magnet 17, andremains energized during the transmission of the impulses. This relay, in attracting its armature, energizes escape magnet 21 by closing the circuit from grounded battery, winding of relay 21, sideswitch arm 22, armature and contact of relay 16 to ground.

The armature of primary magnet 17 is provided with a stepping pawl 23, which engages the vertical ratchet 24 on the brush shaft 40, andmoves the shaft vertically to position a set of brushes 25, 26 and 27 in operative relation to the desired trunk group.

hen the sender 11 restores and maintains the line circuit closed, slow release relay 16, after a short interval, becomes deenergized and opens at its armature and front contact the circuit of escape'magnet 21, which deenergizes and moves the side-switch wipers into position 2. f

In position 2, the following circuit is closed for the secondary magnet 28 to drive the positioned set of brushes over the selected trunk group: grounded battery, contacts 29, conductor 30, winding of magnet 28, contacts 44, conductor 31, side-switch wiper 32 (position 2), conductor 83, armature and front contact of relay 7 to ground.

The armature of magnet 28 is provided with a stepping pawl 24, which engages a rotary ratchet to rotate shaft40.

In position 2 of the side switch, arm 22 connects the escape magnet 21 to the test brush 27 The escape magnet is constructed to release the side switch from position 2 into position 3 upon its energization when the first idle trunk is reached, the idle trunks being those whose test terminals are grounded.

Since magnet 28 opens its own circuit'at contact 44 each time it is energized, the'shaft is rotated step by step until the first idle trunk is reached, at which time the escape magnet 21 becomes energized over the following circuit to move the side-switch wipers into position 3: grounded battery, winding of magnet 21, side-switch arm 22 (position 2), conductor 36, test brush 27 and thegrounded test terminal of the idle trunk. By moving out of'position 2, the side-switch arms 8 and 14 disconnect the stepping relay? from the'conductors'9 and 13, and extend the calling line through to the talking brushes 25 and 26 of the selector. In position 3, the side-switch arm 37 connects the release magnet 41 to the release wire 36 to'prepare the release circuit, which is closed upon the terminationof the 'conversation;

The vertical ratchet 24 is normally engaged bya holding pawl 38, and the rotary ratchet 35 by a holding pawl 39,'these pawls being pivoted upon a pin 42. Upon the replacement of the receivers, ground is placed upon "the release wire 36' leading from the connector in a manner well-known in the art, and closes the circuit of release magnet 41 from grounded battery, winding of magnet 41, primary off-normal contacts 45, sideswitch arm 37 (position 3), to groundover the test wire 36. This magnet, in attracting its armature 46, withdraws the rotary holding pawl 39 from engagement with rotary I ratchet 35, and an arm 47 of this pawl en-' gages an arm 58 to withdraw the holding pawl-38 from ratchet 24, to restore the switch to its normal position. The release magnet,f when energized, locks itself/to groundover a 'circuit extending through contact 59, and remains locked up until the brush shaft 40 reaches its normal position and opens oif-n'ormalcontacts 45.

If, during the secondary movement of the selector, an idle trunk is not found and the secondary magnet 2S drives .the brushes over the terminals of theentire group, a pin48 j I on the brush shaft 40 engages, as the brushes 7 V f group, a pin'49 'onia member 54 pivoted at leave-the terminals of the last trunk. of the I 50to'the' frame of the switch. x Themember 1:54 isgrven a slight rotation in a clockwise direction, as viewed in the drawingsfand causes the pro ectlon 51 thereon'to engage selector.

i an arm 55 of the pawl 39. The pawl 39 is thereby withdrawn from the rotary ratchet .35 to allow the shaft 40 and the brushes secured thereto to be returned to their normal rotary position by a spring (not shown), but the pawl 39 is not moved far enough at this time to cause the arm 47 to engage the arm58 of the vertical holding pawl 38, and

withdraw it from vertical ratchet 24, as is the case'when released magnet 41 is energized. far enough to close contacts 59 to complete the circuit of release magnet 41.

A button 56, of insulating materiah'on the member 54 is arranged to open contacts 29 when the member 54 is in its operated position, and thereby'opens the circuit of the secondary magnet 28 to prevent it from operating during the restoring movement of the switch.

Neither is the armature 46 moved 7 The member 54 is held in this operated of the selected groups in search of an idle trunk. V

The line of action of spring '57 is now on the opposite side of pivot 50 from what it was when the member 54 was in its oper ated position, and therefore serves to keep the member 54 in'its normal position.

The operation just described continues until an idle trunk is found or until the call ing party replaces his receiver, thereby energizing the release magnet 41 to release the The circuit of the release magnet in this case is from grounded battery, winding 'of relay 41, contact 45, side-switch arm 37 in its second position, armature and back contact of relay 15, conductor 20, armature and back contact of relay 7 to ground.

WVhat is claimed is:

1. In a telephone system, an automatic switch, a group of lines terminating in contacts of said switch, means for driving said automatic switch over the contacts of said group, me'ans for causing said. switch to stop upon a set of electrically distinguished contacts, a ratchet, a pawl normally in en- 7 gagement with said ratchet for holding' said switch in its actuated position, and me chanical means operated when said automatic switch reaches'a predetermined posiratchet to allow said switch to restore to its 'normal position whereupon it is again tion for withdrawing said pawl from said switch, a group of lines terminating in a row of contacts of said switch, means for driving said automatic switch over the entire row of said terminals, a ratchet, a pawl normally in engagement with said ratchet for preventing the restoration of said switch, means for causing said switch to stop upon a set of electrically distinguished contacts, and mechanical means operated when said automatic switch reaches the end of said row to withdraw said pawl from said ratchet to allow said switch to return to the beginning of said row, whereupon said switch is again driven over said row.

3. In a telephone system, in combination with telephone lines, an automatic switch, means for associating said lines with said automatic switch, trunk groups terminating in contacts of said switch, means for operating said switch to place it in operative relation to the contacts of a trunk group, automatic means for driving said switch over the contacts of said trunk group, means for stopping said switch on the contacts of the first idle trunk of said group, and mechanical means operated when the switch moves ofi the contacts of the last trunk in said group for restoring said switch in operative relation to the contacts of the first trunk of said trunk group whereupon it is again driven over the contacts of said group in search of an idle trunk.

4. In a telephone system, in combination with telephone lines, an automatic switch, a brush shaft therefor, means for associating calling lines with said switch, primary and secondary magnets for said switch, primary and secondary holding pawls for said brush shaft, a release magnet arranged to withdraw both of said pawls, trunk groups terminating in contacts of said switch, means for operating said primary magnet to set said switch in operative relation to the contacts of a trunk group, automatic means for thereupon operating said secondary magnet for driving the switch over the contacts of said group, means for stopping said switch on the contacts of the first idle trunk of said group, and mechanical means operated by said brush shaft when it reaches a predetermined position for withdrawing said secondary pawl to restore said automatic switch in operative relation to the contacts of the first trunk of said trunk group, whereupon it is again driven over said group in search of an idle trunk.

5. In atelephone exchange system, in combination with telephone lines, a selector, means for associating calling lines with said selector, trunk groups terminating in said se lector, primary and secondary driving magnets for said selector, means for operating said primary magnet to set said selector in operative relation to a trunk group, automatic means for thereupon operating said second ary magnet to drive the selector over said group, means for stopping the selector on the first idle trunk, and mechanical means operated when the selector fails to find an idle trunk in said group for restoring said selector in operative relation to said trunk group, whereupon it is again driven over said group.

6. In a telephone system, in combination with telephone lines, an automatic switch, a brush shaft therefor, means for associating calling lines with said switch, primary and secondary magnets for said switch, a driving circuit for said secondary magnet, primary and secondary holding pawls for said brush shaft, a release magnet arranged to withdraw both of said pawls, trunk groups terminating in contacts of said switch, means for operating said primary magnet to set said switch in operative relation to the contacts of a trunk group, means for thereupon closing said driving circuit for said secondary magnet, means for stopping said switch on the contacts of the first idle trunk of said group, mechanical means operated by said brush shaft when it reaches a predetermined position for opening the driving circuit of said secondary magnet and for withdrawing said secondary pawl to restore said automatic switch in operative relation to the contacts of the first trunk of said trunk group, and mechanical means for closing the driving circuit of said secondary magnet to again drive said brushes over said group in search of an idle trunk and for releasing said secondary pawl when said switch reaches the contacts of the first trunk of said group.

In witness whereof, I hereunto subscribe my name this 27th day of March A. D., 1917.

CHARLES L. GOODRUM.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. 6. 

